Rhododendron ponticum invades three habitats that are considered internationally important under the Habitats Directive: upland oak woods, bogs and heath.
An individual Rhododendron ponticum casts such deep shade that it light-starves out existing native plant colonies at its base. Insult to injury – It also secretes allelopathic toxins which retard germination and regeneration of native plant species nearby.
Given that rhododendrons have a tendency to forms stands and dense thickets the problem of indigenous flora displacement is compounded.
The plant impacts adversely on local fauna too – by displacement of their usual food supply and altering of natural habitat cover. Furthermore the foliage and tissues of Rhododendron ponticum contains quite high concentrations of toxic phenols, which are deadly if ingested by browsing wildlife and other herbivores.
Rhododendron ponticum is also host to the plant fungus Phytophthora ramorum which is the causative agent of “Sudden Oak Death”. It may be beautiful in flower and there is the Darwin argument but really it is time to look at reversing its spread and well tolled damage.
Traditional methods of control can be viewed at http://www.killarneynationalpark.ie/Rhododendron.htm
Untraditional methods – future uses
see more in this blogs invasive species counterattack category